Skoda Fabia II 2009 P0303 Bad Idling

The engine was shaking. I read the fault codes by OBD2 fault codes reader and I got the code P0303 which means misfiring in cylinder 3.
This could be the result because of two reasons, either a faulty ignition coil or a faulty spark plug.
I started with shifting the ignition coil between cylinders 2 and 3, cleared the fault code, started the engine, and read the fault codes again. It is still P0303 which means this has nothing to do with the ignition coil or the coil is working good. If we are supposed to get P0302 that means a faulty ignition coil that moved to cylinder 2 but in this case, it's still P0303 which means that there is something wrong with the spark plug.
I tried another way to figure out the problem by changing the spark plug itself with another one that I already had. I cleared the fault codes again just before I started the engine. I started the engine and it was idling perfectly. I read the fault codes one more time just to be sure that there is nothing registered in the ECU and I found nothing stored.
The problem is solved permanently!! It was just a matter of a faulty spark plug in cylinder 3.